This paper combines Genetic Algorithm with Simulated Annealing Algorithm, namely GA-SA，to discuss vehicle paths and take into account the condition of time with respect to multi-spot service combination problem in service centre. The prevalent genetic algorithms easily lose the optimal solution, which affects the entire algorithm performance for reality vehicle assignment problem in the service centre. Based on modelling the vehicle assignment problem with natural description, fitness function, crossover operation and mutation operation are made the improvement in the approach. The process of computation has also considered own characteristics of the service centre to enable the algorithm optimized performance, in order to obtain the large scale enhancement.